1. Field of Invention
This invention relates generally to the field of projection apparatus and more particularly to a screen projection apparatus capable of unrolling one of a plurality of screens for projection, and more specifically to a screen projection apparatus for unrolling one of a plurality of screens for projection at the same optical plane.
2. Description of the Prior Art
The prior art related to projection screens includes apparatus in which a screen is stored rolled on a motor driven roller within a housing. During operation, the motor is energized and the screen is unrolled. When projection is completed, the screen is rerolled on the roller. The projection screen apparatus of the prior art is adapted for the storage and display of a single size screen. In the event that a second size, or second type of screen is required, extensive rework of the installation is required. Attempts to provide a second screen capability through the utilization of a temporary screen are usually unsatisfactory as a result of the difficultly in locating the second screen with sufficient accuracy at the same optical plane, therefore resulting in a need to refocus the projection apparatus and often to make compromises in the focusing operation with results that are usually only marginally acceptable.